What are the purposes of an experiment is to determine whether the dependent variable affects the independent variable?

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Before you start your experiment, you need to have a clear definition of, and strategy for, how each variable will be measured and recorded. This process is called variable operationalization.

For example, you are interested in studying attitudes towards food, visual attention, and food choice. In your first study, your objective is to investigate “the effect of personal health goals on visual attention to different food groups”.

The first part of your objective, “the effect of personal health goals…”, contains an independent variable. To operationalize it you need to ask yourself the following questions: What is a personal health goal? Can you quantify and measure it? Can you break it down into distinct categories? How will you collect and record its value? Due to the nature of this term, your variable will most likely be composed of two or more categories (e.g. lose weight, keep weight, gain weight etc.) and its value recorded by means of a questionnaire or interview. Notice that in this example, the independent variable is also an intrinsic attribute of a participant and thus particular to that individual, as a result, this variable can also be classified as a participant variable.

The next part of your study objective “…on visual attention to different food groups”, contains your dependent variable. Once again, you will need to ask yourself the following questions: What is visual attention? How do I measure it? How is food grouped? How will we represent the different groups in the stimuli? Which grouping strategy is relevant to my objective? The term “visual attention to” can be operationalized into one or more relevant visual behavior measures that can be quantified and measured continuously. For example, eye tracking metrics like fixation duration, fixation count, and dwell time can provide you with information about the visual engagement and bias towards different items in your stimulus. The “… different food groups” term will most likely be operationalized as food types aggregated into categories (e.g. vegetables, red meat, dairy) and displayed on an image stimulus. Since you are manipulating the content of the stimulus and the manipulation affects the context in which the behavior occurs as well as the viewing behavior itself, your stimulus categories will be part of your set of independent variables and simultaneously a stimulus variable.

The dependent variable is the variable that is being measured or tested in an experiment. For example, in a study looking at how tutoring impacts test scores, the dependent variable would be the participants' test scores since that is what is being measured.

This is different than the independent variable in an experiment, which is a variable that stands on its own. In the example above, the independent variable would be tutoring. The independent variable (tutoring) doesn't change based on other variables, but the dependent variable (test scores) may.

One way to help identify the dependent variable is to remember that it depends on the independent variable. When researchers make changes to the independent variable, they then measure any resulting changes to the dependent variable.

The dependent variable is called "dependent" because it is thought to depend, in some way, on the variations of the independent variable.

In a psychology experiment, researchers study how changes in one variable (the independent variable) change another variable (the dependent variable). Manipulating independent variables and measuring the effect on dependent variables allows researchers to draw conclusions about cause-and-effect relationships.

These experiments can range from simple to quite complicated, so it can sometimes be a bit confusing to know how to identify the independent vs. dependent variables. Here are a couple of questions to ask to help you learn which is which.

Keep in mind that the dependent variable is the one being measured. So, if the experiment is trying to see how one variable affects another, the variable that is being affected is the dependent variable.

In many psychology experiments and studies, the dependent variable is a measure of a certain aspect of a participant's behavior. In an experiment looking at how sleep affects test performance, the dependent variable would be test performance.

The independent variable is "independent" because the experimenters are free to vary it as they need. This might mean changing the amount, duration, or type of variable that the participants in the study receive as a treatment or condition.

For example, it's common for treatment-based studies to have some subjects receive a certain treatment while others receive no treatment at all. In this case, the treatment is an independent variable because it is the one being manipulated or changed.

Independent Variable

• Variable being manipulated

• Doesn't change based on other variables

• Stands on its own

Dependent Variable

• Variable being measured

• May change based on other variables

• Depends on other variables

How do researchers determine what will be a good dependent variable? There are a few key features that a scientist might consider.

Stability is often a good sign of a higher quality dependent variable. If the experiment is repeated with the same participants, conditions, and experimental manipulations, the effects on the dependent variable should be very close to what they were the first time around.

A researcher might also choose dependent variables based on the complexity of their study. While some studies only have one dependent variable and one independent variable, it is possible to have several of each type.

Researchers might also want to learn how changes in a single independent variable affect several dependent variables. For example, imagine an experiment where a researcher wants to learn how the messiness of a room influences people's creativity levels.

This research might also want to see how the messiness of a room might influence a person's mood. The messiness of a room would be the independent variable and the study would have two dependent variables: level of creativity and mood.

Operationalization is defined as "translating a construct into its manifestation." In simple terms, it refers to how a variable will be measured. So, a good dependent variable is one that you are able to measure.

If measuring burnout, for instance, researchers might decide to use the Maslach Burnout Inventory. If measuring depression, they could use the Patient Health Questionnaire-9 (PHQ-9).

As you are learning to identify the dependent variables in an experiment, it can be helpful to look at examples. Here are just a few dependent variable examples in psychology research.

• How does the amount of time spent studying influence test scores? The test scores would be the dependent variable and the amount of studying would be the independent variable. The researcher could also change the independent variable by instead evaluating how age or gender influences test scores.
• How does stress influence memory? The dependent variable might be scores on a memory test and the independent variable might be exposure to a stressful task.
• How does a specific therapeutic technique influence the symptoms of psychological disorders? In this case, the dependent variable might be defined as the severity of the symptoms a patient is experiencing, while the independent variable would be the use of a specific therapy method.
• Does listening to classical music help students perform better on a math exam? The scores on the math exams are the dependent variable and classical music is the independent variable.
• How long does it take people to respond to different sounds? The length of time it takes participants to respond to a sound is the dependent variable, while the sounds are the independent variable.
• Do first-born children learn to speak at a younger age than second-born children? In this example, the dependent variable is the age at which the child learns to speak and the independent variable is whether the child is first- or second-born.
• How does alcohol use influence reaction time while driving? The amount of alcohol a participant ingests is the independent variable, while their performance on the driving test is the dependent variable.

Understanding what a dependent variable is and how it is used can be helpful for interpreting different types of research that you encounter in different settings. When you are trying to determine which variables are which, remember that the independent variables are the cause while the dependent variables are the effect.

Frequently Asked Questions

• What does the dependent variable depend on?

  The dependent variable depends on the independent variable. Thus, if the independent variable changes, the dependent variable would likely change too.

• Where does the dependent variable go on a graph?

  The dependent variable is placed on a graph's y-axis. This is the vertical line or the line that extends upward. The independent variable is placed on the graph's x-axis or the horizontal line.

• How do you find a dependent variable?

• What is a controlled variable?

  A controlled variable is a variable that doesn't change during the experiment. This enables researchers to assess the relationship between the dependent and independent variables more accurately. For example, if trying to assess the impact of drinking green tea on memory, researchers might ask subjects to drink it at the same time of day. This would be a controlled variable.